Malfunction Phenomenon
The iPhone 7 stuck at recovery mode, and it reported error code 9 when restoring with iTunes.
Trouble Shooting
According to repair experience, error code 9 usually caused by the malfunction of NAND flash U1701 or EEPROM U2301.
We checked the NAND by measuring the voltage on C1721, C1702, and C1730, the value was 3.0V, 0.9V, and 1.8V, which were normal.
Then continue to check the power for EEPROM by measuring the voltage on C1101.
The value was 1.8V, which was also normal.
The power for the NAND and EEPROM were both normal, the problem might be from the data line or the chips. We removed the NAND and checked the pads on the PCB, all the diode values are also normal, then use the NAND reader to check the NAND chip, it was also good.
So we can try to replace another EEPROM U2301.
After replacing another EEPROM, connect with the computer, and tried to restore again, there was no error code anymore and the phone worked normally.
Tips: The Logic EEPROM for iPhone 7/7P can be replaced
iPhone 7 Motherboard Repair Course
